Safety explicit design of freeway speed change lanes

Publication

Publication

Reducing collision frequency on a road network is a fundamental goal of transportation engineers. Recently, research has been oriented toward developing safety-explicit relationships for the evaluation of the impact of highway design decisions. Among the major areas for driver decision, and subsequently areas for potential errors and collisions, are the freeway entrances and exits.. Adequate lengths between entrance and exit terminals, with enough length for speed change lanes, would give drivers enough time to find acceptable gaps, accelerate or decelerate, and merge or diverge properly. This paper presents a comprehensive review of the state-of-practice and state-of-knowledge regarding the length and type of acceleration and deceleration lanes. Then, safety-explicit models are presented as design aids for the length of acceleration and deceleration lanes based on expected collision frequency. Factors such as traffic exposure, advisory speeds on exits, and entering and exiting traffic volume have been considered in the modelling attempts.